There is "little evidence" that the use of conventional fertility hormones used for ovarian stimulation in the treatment of infertility increases the long-term risk of breast and gynecological cancers, according to the results of a substantial 30-year follow-up study. However, the extended use of clomiphene citrate was associated with a higher risk of breast cancer among women who had used the fertility drug for 12 cycles or more. Gonadotrophins, more commonly used for ovarian stimulation today, were not generally associated with any increased risk, except in a sub-group of women who remained childless after treatment.